Discrimination between forms of vitamin E by humans with and without genetic abnormalities of lipoprotein metabolism.

To study the mechanisms of discrimination between various forms of vitamin E, four normal subjects, one patient with lipoprotein lipase deficiency, and three patients with abnor- mal apolipoprotein B-100 production were given an oral dose containing three tocopherols labeled with differing amounts of deuterium (2R,4'R,8'R-a-(5,7-(C2H3)2)tocopheryl acetate (de- RRR-a-tocopheryl acetate), 2S,4'R,8'R-a-5-(C2H3)tocopheryl acetate (d3-SRR-a-tocopheryl acetate), and 2R,4'R,8'R-y- (3,4-2H)tocopherol (d2-RRR-y-tocopherol). The tocopherol con- tents of plasma, red cells, and lipoproteins were measured up to 76 h after the dose. In normal subjects all three tocopherols were absorbed and secreted in chylomicrons with equal efficiencies. Both dz-y- and d3-SRR-a-tocopherols peaked at similar concen- trations in the other lipoprotein fractions, then decreased simi- larly, but 2-4 times more rapidly than did d6-RRR-a-tocopherol. A lipoprotein lipase-deficient patient and a patient with pro- longed production of chylomicrons with absent apolipoprotein B-100 also demonstrated the lack of discrimination between tocopherols during absorption. Despite abnormal apolipopro- tein B-100 production in two patients, the "VLDL" was preferen- tially enriched in d6-RRR-a-tocopherol. fl Our results show that there is no discrimination between the three tocopherols during absorption and secretion in chylomicrons, but subse- quently there is a preferential enrichment of very low density lipoprotein (VLDL) with RRR-a-tocopherol. Catabolism of this VLDL results in the maintenance of plasma RRR-a-tocopherol concentrations.-Traber, M. G., G. W. Burton, L. Hughes, K. U. Ingold, H. Hidaka, M. Malloy, J. Kane, J. Hyams, and H. J. Kayden. Discrimination between forms of vitamin E by humans with and without genetic abnormalities of lipoprotein metabolism. J Lipid Rtx. 1992. 33: 1171-1182.